This invention relates to an electrode tip control method for a welding gun in an automatic welding machine in which the welding gun is moved by a robot successively to a plurality of welding spots on work-in-progress.
In a conventional automatic welding machine, it has been usual to count the number of units of work-in-progress on which a particular electrode tip has been used to perform welding. The tip of the electrode is then reformed by a tip dresser at intervals of a specified number of the welded units. The tip is considered to have come to its usability limit when reformed for a predetermined number of times, and is then replaced with a new one.
An electrode tip is conventionally reformed as follows. The top of the electrode tip which has become enlarged in diameter as a result of the wear during use is cut into a tapered shape until it is reformed to the specified diametral value. The amount of cutting varies depending on the degree of wear of the tip. For this reason, the tip length is not necessarily the same for the electrode tips which have been reformed for the same number of times, so that some of them still retain a usable tip length even after being reformed for the predetermined number of times. Therefore, when an electrode tip is replaced with a new one just because it has been reformed for the predetermined number of times as in the foregoing method, it is possible to throw away a still usable electrode tip, thus resulting in waste.
In view of this problem, it is an object of the present invention to provide an electrode tip control method wherein waste resulting from a premature replacement of an electrode tip is avoided by accurately determining whether or not the actual tip length has become shortened to the usability limit thereof.